Facial Paralysis and Myositis Following the H3N2 Influenza Vaccine in a Dog

A dog (2-year old, female, Shih-Tzu) presented with hyperthermia and right-sided facial paralysis characterized by the inability to close the right eye and drooling from the right side of the mouth after H3N2 influenza vaccination [A/ Canine/Korea/01/07(H3N2) strain; Caniflu-Max, Bionote, Hwaseong, Gyeong-gi-do, ROK]. To determine the cause of the fever and neurological symptoms, physical examination, ophthalmic examination, thoracic and abdominal radiog-raphy, abdominal ultrasonography, complete blood counts, serum chemistry values, and electrolyte levels were determined. In addition, Cerebrospinal fluid analysis, antinuclear antibody test, fever of unknown origin polymerase chain reaction (PCR) panel, tick-borne pathogen PCR panel were performed. As a result, hyperthermia, leukocytosis, and elevated C-reactive protein were confirmed. In addition, neurological examination revealed decreased right eyelid reflexes, corneal reflexes, threat response, and facial sensation, it was possible to suspect problems with the trigeminal and facial nerves of the cranial nerve. Magnetic resonance imaging revealed a lesion suggestive of myositis in the right muscular lesion at atlanto-occipital junction level on site of vaccine injection. Therefore, right-sided facial paralysis was tentatively determined to be a secondary cause of nerve damage caused by myositis. The patient was treated with immunosup-pressants such as prednisolone and mycophenolate mofetil. After 3 months of immunosuppressant therapy, the patient’s symptoms improved.